Slit lamp

ABSTRACT

A slit lamp in which a telecondenser is connected behind the incandescent lamp which consists of several positive and at least one negative lens element whereby a slot diaphragm is arranged close to the last negative lens of the telecondenser.

United States Patent 1 Wilms SLIT LAMP [75] Inventor: Karl-Heinz Wilrns,Munich, Germany [73] Assignee: Optische Werke G. Rodenstock, Munich,Germany 22 Filed: 061. 9, 1970 21 App1.No.: 79,547

[30] Foreign Application Priority Data Oct. 29, 1969 Germany ..P 19 54312.5

[52] U.S. Cl. ..240/4L3, 128/6, 128/23, 240/2 M, 240/41.15

[51] Int. Cl. ..F2lv 13/04 [58] Field of Search 240/41.3,41.15, 240/41R, 1 R, 2 R, 2 M; 128/6, 395, 23;

[ 1 May 22, 1973 [56] References Cited UNITED STATES PATENTS 3,533,68510/1970 Littmann 61 al ..351/14 3,405,994 10/1968 Altman 61 a1 ..351/143,407,019 10/1968 Wilkinson ..351/14 3,586,424 6/1971 Schenk 61 a1...351/14 1,680,663 8/1928 Campbell .351/14 x Primary Examiner-Richard L.Moses Att0meyCraig, Antonelli, Stewart & Hill 5 7 ABSTRACT A slit lampin which a telecondenser is connected bebind the incandescent lamp whichconsists of several positive and at least one negative lens elementwhereby a slot diaphragm is arranged close to the last negative lens ofthe telecondenser.

7 Claims, 2 Drawing Figures SLIT LAMP The present invention relates toan illumination installation for slit lamps with a high light-yield.

Slit lamps project into the forward part of an eye to be examined abright slit whereby details are observed in the illuminated portions bymeans of a microscope. It is necessary in that connection for the exactobservation of the illuminated eye portion that the slit lamp produce aphotometric output as high as possible.

I-Ieretofore incandescent lamps of 25 to 30 Watts have been used forthat purpose. However, the incandescent lamps of this power produce aconsiderable amount of heat which is undesirable especially on theadjacent adjustable slot diaphragm. Simultaneously therewith, arelatively slight structural length of the illuminating optics isdesirable in order to improve the handling of slit lamps.

The present invention provides a slit lamp in which a high light-yieldproducing only a slight amount of heat and with simultaneous smallstructural length of the illumination apparatus. This is achievedaccording to the present invention by the use of a telecondensercomprising an assymetrical lens arrangement having a relatively strongnegative lens on the side of the image is subdivided in one embodimentinto two lenses of which the first lens is arranged in front of the slotdiaphragm and the second behind the slit group in the direction ofnormal passage of the rays through the apparatus. The negative lensbehind the slot diaphragm thereby acts as an image-field flatteningelement between the slit and the adjoining objective. This secondnegative lens which is arranged as close as possible behind the slotdiaphragm acts simultaneously as an element of the objective or lensconnected behind the slot diaphragm which thus effectively becomes ateleobjective.

By this arrangement which additionally is characterized by a distinctlyslight structural length, a very high magnification of the incandescentlamp filament (about times) can be achieved which leads to aparticularly high photometric output of the slit lamp. The condensermagnification makes it possible to achieve with an incandescent lamp ofonly 15 Watts of input power, an intensity of illumination or brightnessin the slit image of about A million lumens whereby the bright slitimage is 8.5 mm. long.

In another embodiment of the present invention, the negative lens of thetelecondenser on the image side is not subdivided so that the slotdiaphragm lies between the last positive element and the negativeelement on the image side of the telecondenser. The negative lens of thetelecondenser again cooperates with the seriesconnected objective whichhas thus also been constituted a tele-objective.

In both cases the negative condenser element is utilized in the mannerof a Smith lens for the elimination of the image-field curvature of theobjective which is series-connected behind the same. The slit image isthereby reproduced well-flattened on the eye portion.

Accordingly, it is an object of the present invention to provide anillumination apparatus for slit lamps which avoids by simple means theaforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in a slit lamp whichassures a relatively high light output without the production of anundesirable, excessively large amount of heat.

A further object of the present invention resides in an opticalapparatus of the type described above which can be easily manipulatedand, at the same time, provides an improved light intensity as well asvery small image curvature.

These and other objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, two embodiments in accordance with thepresent invention, and wherein:

FIG. 1 is a somewhat schematic cross-sectional view of a firstembodiment of an illumination installation for slit lamps in accordancewith the present invention with a sub-divided negative lens of thetelecondenser; and

FIG. 2 is a somewhat schematic cross-sectional view through a secondembodiment of an illumination installation for slit lamps in accordancewith the present invention with a unitary negative lens made in one partof the telecondenser.

Referring now to the drawing wherein like reference numerals are usedthroughout the various views to designate like parts and moreparticularly to FIG. 1, reference numeral 1 designates in this figure aconventional incandescent lamp to which is coordinated a telecondenser 2that contains a conventional slot diaphragm 3 intermediate thesub-divided negative lens elements 2c and 2d arranged on the two sidesof the slot diaphragm 3. The slit image 3' is projected into the eye tobe examined, by an objective 4 of conventional construction,series-connected behind the telecondenser 2, and by a deflecting prism5. The negative lens 2d arranged behind the slot diaphragm 3 in thenormal direction of travel of the rays acts simultaneously as an elementof the objective 4. This brings about a particularly spacesavingarrangement of the objective 4 which becomes thereby in its effect atele-objective.

The embodiment of FIG. 2 is substantially similar to that of FIG. 1 withthe only difference that the negative element of the telecondenser 2 isnot sub-divided so that the slot diaphragm 3 is arranged between thepositive lens elements 2a and the single negative lens element 2b of thetelecondenser 2.

Since the various lens elements and parts of the optical apparatus shownand described in connection with FIGS. 1 and 2 are conventional, adetailed description thereof is dispensed with herein for the sake ofunnecessary duplication. It might be mentioned that the variouslenselements are designed in accordance with conventional, existingpractices for the type of lenses involved, utilizing conventionalglasses as also generally known.

While I have shown and described only two embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art, and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

What I claim is:

1. A slit lamp comprising:

a light source;

I that the light source is an incandescent lamp.

A slit lamp according to claim 1, characterized in that said at leastone negative lens element consists of two negative lenses which arearranged on the two sides of said slot diaphragm in the direction ofpassage of the light rays.

4. A slit lamp according to claim 1, characterized in that said slotdiaphragm is arranged between the positive elements, on the one hand,and a single negative element.

5. A slit lamp with an objective downstream of said assymmetrical lensarrangement, according to claim 4, characterized in that the negativelens downstream of said slot diaphragm assumes together with theobjective the function of a tele-objective and simultaneously serves asan image flattening lens in connection with the reproduction of saidslot diaphragm.

6. A slit lamp according to claim 5, characterized in that said at leastone negative lens element consists of two negative lenses which arearranged on the two sides of said slot diaphragm in the direction ofpassage of the light rays.

7. A slit lamp according to claim 5, characterized in that said slotdiaphragm is arranged between the positive elements, on the one hand,and a single negative element.

1. A slit lamp comprising: a light source; an assymmetrical lensarrangement disposed to direct the light from said light source along aprescribed path, said assymmetrical lens arrangement including aplurality of positive lens elements disposed adjacent one another, andat least one negative lens element disposed on the side of saidplurality of positive lens elements downstream of said light source; anda slot diaphragm disposed adjacent said at least one negative lenselement.
 2. A slit lamp according to claim 1, characterized in that thelight source is an incandescent lamp.
 3. A slit lamp according to claim1, characterized in that said at least one negative lens elementconsists of two negative lenses which are arranged on the two sides ofsaid slot diaphragm in the direction of passage of the light rays.
 4. Aslit lamp according to claim 1, characterized in that said slotdiaphragm is arranged between the positive elements, on the one hand,and a single negative element.
 5. A slit lamp with an objectivedownstream of said assymmetrical lens arrangement, according to claim 4,characterized in that the negative lens downstream of said slotdiaphragm assumes together with the objective the function of atele-objective and simultaneously serves as an image flattening lens inconnection with the reproduction of said slot diaphragm.
 6. A slit lampaccording to claim 5, characterized in that said at least one negativelens element consists of two negative lenses which are arranged on thetwo sides of said slot diaphragm in the direction of passage of thelight rays.
 7. A slit lamp according to claim 5, characterized in thatsaid slot diaphragm is arranged between the positive elements, on theone hand, and a single negative element.